Among other fluorine resins, because the perfluoro polymer that is particularly represented by the copolymer (PFA) of tetrafluoroethylene (TFE) and perfluoro (alkyl vinyl ether) and (PAVE) has the characteristics of superior heat resistance, chemical resistance, purity, dielectric constant and so on, this polymer is used for melt-molding of piping for transporting various chemicals, joints of piping, transportation containers, storage containers, pumps and filter housings, and so on in chemical plants and semiconductors or the manufacturing process of the liquid products; and is used for lining electronic boards, steel pipes, pulps, fittings and so on.
However, because generally these perfluoro polymers are insoluble, these polymers are being used in various applications in the method of so-called hot melt molding.
In order to give the characteristics of this fluorine resin to various base materials, attempts were made to dissolve the amorphous fluorine resin in a solvent. For example, it has been proposed that the amorphous tetrafluoroethylene copolymer is dissolved and dispersed in the monoalkoxy-substituted solvent of the perfluoroalkane and so on, to be the composition of the coatings. Moreover, it has been proposed that the amorphous fluorine-containing resin that has the fluorine-containing aliphatic cyclic structure in the main chain is dissolved in a specific perfluoro solvent, for example, perfluoro (2-butyl tetrahydrofuran); and then the thin films of the fluorine-containing polymer free from pinholes can be formed from the perfluoro solvent solution of this fluorine-containing polymer. (Patent document 1, Patent document 2, and Patent document 3).
However, the fluorine-containing solvents of perfluoroalkane, hydrofluorocarbon, hydrofluoroether, and so on that are used in the prior art have high global warming potential, and cannot satisfy the requirements from the perspective of the efforts to protect the global environment (refer to Table 1 mentioned below).